Signal that protects rice from blight bacteria

Researchers
have identified the underlying signaling pathway that provides disease
resistance to rice against the leaf blight bacteria Xanthomanas oryzae1. They suggest that instead of
relying on pesticides, this signaling system could be exploited to stimulate the
plant defense mechanism and weaken the bacteria.

The
researchers studied the mitogen activated protein kinases (MAPK) signaling in
rice and how it confers resistance against the bacteria notorious for causing
leaf blight disease. The widely-studied MAPK signaling cascade gets activated
during both biotic and abiotic stress in plants.

Pathogens
have evolutionarily conserved structures recognized by receptors on the plant
outer membrane. These receptors, when activated, cascade a signaling trigger
that abates the pathogen. Alok Krishna Sinha and Siddhi K Jalmi at the National
Institute of Plant Genome Research in New Delhi have been working on
understanding such signaling and the plant’s counter response when the pathogen
challenges a rice host.

They
looked at the role of three members of the MAPK family – OsMKK3, OsMPK7 and OsWRK30 – in the
plant’s immune response against Xanthomonas
oryzae. When OsMPK7 was over expressed, the researchers saw a marked
decrease in lesions caused by the pathogen. Over expression of OsMKK3 and OsWRK30 also helped in conferring resistance. Sinha says this can
be attributed to the activation of immune response genes and strengthening of
the cell wall.

Silencing
of these MAPK members causes an increase in disease conditions. The researchers
now plan to extend the experiments, performed in greenhouse conditions, to transgenics
that over-express OsMPK7 in field conditions.